During the manufacture of polycaprolactam and polycaprolactam articles, recycling of polycaprolactam articles and cleaning operations of reactors and processing machinery, caprolactam emissions may be released to the environment, which is not desirable. For example, before, during and after the polymerization of epsilon-caprolactam, hereinafter referred to as caprolactam, monomer vapors may be released in the environment from transportation tanks, storage tanks, pipelines, ducts, polymerization reactors, polymer melts, polymer strands, water bath, cutters, dryers and the like. During thermoplastic polycaprolactam processing like injection molding or extrusion the thermoplastic polymers are for example extruded through an extruder into strands for chip production or into films, fibers, profiles, tubes and the like. During the extrusion at a temperature of from about 180.degree. to about 350.degree. C., monomer or oligomer caprolactam vapors, compounds formed by thermal evaporation, thermal decomposition, or vapors of additives are released from the surface of the extruded polymers, which are leaving the nozzle of the extruder. These vapors evaporate immediately into an aerosol that would form deposits in the neighborhood of the extruder and therefore must be removed, which is usually done by the quench air removal. The exhaust air is usually released into the environment, which is not desirable.
A filament quenching apparatus is known from U.S. Pat. No. 3,619,452 which comprises a quenching chamber and a gas entry chamber. The quench air exits the quenching apparatus without further treatment.
U.S. Pat. No. 4,676,807 discloses a process for removal of liquid aerosols from gaseous streams by passing the stream through a coalescing filter. In the examples oil and water aerosols were tested.
U.S. Pat. No. 4,759,782 which is a C.I.P. of an application which issued as U.S. Pat. No. 4,676,807 described above, discloses the coalescing filter for removal of liquid aerosols from gaseous streams.
U.S. Pat No. 4,464,266 discloses a process for removing caprolactam and its oligomers from cooling water in order to prevent algal growth by introducing gases into the cooling water and separating off the formed foam. Other procedures for preventing algal growth were the addition of colloidal silver, ozonization of water and addition of formaldehyde, all of which may damage the nylon 6.
U.S. Pat. No. 5,219,585 discloses a monomer exhaust system for exhausting fumes released from a melt spinning process which has a housing, a nozzle for the collection of the fumes, a duct, a drawing force for moving the fumes and rinsing means for automatically purging said exhaust system of condensed fume deposits.
An object of the present invention was to provide a process for removal of emissions from caprolactam polymerization operations and thermoplastic polycaprolactam processing operations, which overcomes the problem of biological growth in the removal system.
Another object was to remove emissions from polycaprolactam fiber spinning operations, which overcomes the problem of biological growth in the removal system.